The present invention relates to a semiconductor device and a communication device for communication control. More specifically, the present invention relates to a technology that is appropriately applicable to IC cards and the other NFC (Near Field Communication) terminals designed for electromagnetic induction communication.
There are several currently available IC card systems having non-contact interfaces. Examples include ISO14443-A (type-A system) and ISO14443-B (type-B system) standardized by ISO, and the high-speed IC card system (referred to as high-speed type) standardized by Japan IC Card System Application Council (JICSAP).
During data transfer from a reader/writer to the IC card, for example, the type-A system pauses an RF (Radio Frequency) operating magnetic field and performs 100% ASK (amplitude shift keying) modulation. A Modified Miller code is used for modulated signals.
During data transfer from a reader/writer to the IC card, for example, the type-B system performs 10% ASK modulation on the RF operating magnetic field. An NRZ (Non Return to Zero) code is used for modulated signals.
During data transfer between a reader/writer and the IC card, for example, the high-speed type performs 10% ASK modulation on the RF operating magnetic field. A Manchester code is used for modulated signals.
For communication using multiple communication systems, a communication terminal such as the IC card has decoders compatible with the communication systems. The communication terminal such as the IC card uses a determination circuit to determine whether or not the decoders successfully decode data. A selection circuit needs to select an output from the decoder that successfully decodes data. Patent Document 1 describes an example of providing a reader/writer with multiple decoding circuits and selection circuits in accordance with communication systems.
Patent Document 1: Japanese patent laid-open No. 2002-342725